In 2015, end-use markets consumed 87.9% percent by weight of the scrap tires generated in the U.S. The total volume of scrap tires consumed in end use markets in the U.S. reached approximately 3551 thousand tons of tires. RMA estimates that about 4038 thousand tons of tires were generated in the U.S. in 2015. Of those tires, 25.8% were used to produce ground rubber, 48.6% for tire derived fuel, 11.4% were land disposed, 7.0% were used in civil engineering, and 7.1% went to miscellaneous uses (0.7% to electric arc furnace, 1.3% to reclamation projects, 2.6% were exported, and 2.6% went to other uses). In 1990, only eleven percent of tires were consumed on a per tire basis. Positive end-use market results in 2015 were primarily the result of high rates of TDF use and lower exports. In the long term, the need to expand all economically viable and environmentally sound markets for scrap tires is still an imperative. Scrap tires were consumed by a variety of scrap tire markets, including tire-derived fuel, civil engineering and ground rubber applications. Other smaller markets and legal landfilling consumed the remaining annually-generated tires.
Key scrap tire markets include tire derived fuel, ground rubber, civil engineering and other markets. In tire derived fuel applications, scrap tires are used as a cleaner and more economical alternative to coal as fuel in cement kilns, pulp and paper mills and industrial and utility boilers. Ground rubber applications utilize approximately 1020 thousand tons of scrap tires, or over 25 percent of the volume of scrap tires generated each year. Ground rubber is produced by grinding scrap tires into size defined pieces. Ground rubber applications include new rubber products, playground and other sports surfacing and rubber-modified asphalt. Ground rubber also includes larger pieces of rubber used as landscaping mulch, and loose fill playground material. The playground and mulch market was the most dynamic segment in the ground rubber market during this period. The asphalt market uses ground rubber to modify the asphalt binder used in road paving, resulting in quieter, more durable roads. The civil engineering market consumes approximately 274 thousand tons of tires per year, about 7.7 percent of the total tires to market, and consists of tire shreds used in road and landfill construction, septic tank leach fields, alternative daily cover and other construction applications. Additional smaller markets for scrap tires exist that consume approximately 7% of annually generated scrap tires. These markets include tires consumed in electric arc furnaces (steel manufacturing), professionally engineered tire bales and products punched, pressed or stamped from scrap tires. Total tire rubber consumed in ground rubber markets is about 1.36 billion pounds. The total scrap tires diverted to these ground rubber markets is about 1.02 million tons (62 million tires). The percent of total pounds of ground rubber consumed in the market in 2015 is as follows: sport surfaces 25%, playground mulch 22%, molded/extruded products 35%, asphalt 15%, automotive uses 2%, and export 1%.
Stockpiles of scrap tires historically began to be created around the 1960s and 1970s when tires were diverted from landfills, but recycling markets for them were not functional. Stockpiles proved to be prone to catastrophic fires which created air and water pollution.
Worldwide rubber tire production is responsible for generating approximately 99% of worldwide, end-of-life (EOL) tire scrap. About 1.1 billion scrap tires are generated annually, corresponding to roughly 12 million tons of scrap tire. Due to the punishing physical properties required of a new tire, tires embody a carefully engineered weaving together of steel and fiber cords with a mineral and carbon-filled rubber blend, all cross linked to a highly tenacious structure. The EOL tire is challenging to breakdown to its original essential elements. The potentially highest value component—the rubber—is particularly difficult to reclaim, due to the vulcanization process it is subjected to. As a result EOL tires that are no longer suitable for use on vehicles due to wear or irreparable damage are typically either subject to pyrolysis (e.g., to generate energy for use in cement manufacturing), or ground up to be used as filler (e.g., in asphalt pavement, new tires, construction or landscaping materials).